With rapid development of semiconductor fabrication technology, semiconductor devices are advanced in a direction of having higher component density, higher integration level, and better performance.
Laterally diffused metal-oxide-semiconductor (LDMOS) device is a power device with a double-diffused structure. The LDMOS device is typically fabricated by performing two ion implantation processes onto a substrate. For example, one implantation process may introduce arsenic (As) ions with a relatively high concentration into the substrate, while the other implantation process may introduce boron (B) ions with a relatively low concentration. After performing the two ion implantation processes, a high temperature annealing process is performed. During the high temperature annealing process, boron ions often diffuse quicker than arsenic ions. Therefore, along a lateral direction under the gate electrode, boron ions may diffuse further than arsenic ions, and thus form a channel with a concentration gradient. The length of the channel is determined by the difference between the diffusion lengths of the two types of ions along the lateral direction. Moreover, in order to increase the breakdown voltage, a drift region may be formed between the source region and the drain region of the device.
The drift region in LDMOS devices is the key to the design of the devices. The impurity concentration in the drift region is relatively low. When an LDMOS device receives a high voltage, the device may be able to sustain such a high voltage because of the high resistance of the drift region. Moreover, LDMOS devices demonstrate advantages including high gain, high reliability, etc. and may also show desired process compatibility with existing CMOS devices, and thus LDMOS devices are widely used in various fields.
However, the gate dielectric layer in existing LDMOS devices may be easily broken down. The disclosed semiconductor structures and fabrication methods thereof are directed to solve one or more problems set forth above and other problems in the art.